Camacho inlet southern Brazil e Instability causes and user conflicts Guilherme Vieira da Silva, João Luiz Baptista de Carvalho, Antonio Henrique da Fontoura Klein * Universidade de Santa Catarina, UFSC, Laboratório de Oceanografia Costeira, Campus Universitário, Trindade, Florianópolis, SC 88040-900, Brazil article info Article history: Available online xxx abstract Inlet stabilization is a common practice in Brazil, as it is worldwide. In this paper we present results of the analysis of the stabilization practices of the Camacho Inlet, located in Santa Catarina State, southern Brazil. This inlet is maintained intermittently, in accordance with a regime designed to benefit both local fishermen and rice farmers. Fishermen require this inlet to be open as a navigation channel during the fishing season; rice farmers needs it closed during the irrigation period to allow the pumping of fresh water from the Congonhas River which drains into the Camacho’s backbarrier lagoon. An additional complication arises from the tendency of this inlet to close naturally due to infilling by dune migration. Aerial images spanning a 65 year time period (1938e2003) were analyzed, demonstrating the variability in the inlet’s width between 0 (closed) and 360 m. The analysis of inlet stability and user needs indicate that an appropriate solution is the implementation of an annual inlet dredging program in the austral autumn. This would allow for the inlet to remain open from May to September and then close naturally for the rest of the year, providing for a backbarrier fresh water reservoir during the irrigation period. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction About two-thirds of the world’s population lives within the narrow belt directly landward of the ocean (Komar, 1996). According to Deudall and Maul (2005), 48.6% of the Brazilian population lives within 100 km of the sea. This population relies on access to ocean resources, which occurs dominantly through tidal inlets, the connectors between the open ocean and bays, estuaries or lagoons. Komar (Komar, 1996) considers inlets the most complex environment within the coastal zone, and coastal and estuarine engineers have paid particular attention to these features because of their commercial, recreational and ecological importance e.g. (U.S. Army Corps of Engineers, 2002; Davis and Fitzgerald, 2004; Komar, 1998, Militello and Hughes, 2000; Vila-Concejo et al., 2002). Because of their complexity and human and environmental importance, studies of inlet stability and inlet engineering have become increasingly important in recent years. The concept of inlet stability addresses the equilibrium potential between the inlet cross sectional area and the volume of water and sediment trans- port (Jain et al., 2004). There are two types of inlet stability: 1) plan- view stability: stability against migration of the inlet along the shoreline (this paper); and 2) stability against a reduction in cross sectional area or inlet closure (Goodwin, 1996; Borderes de Oliveira et al., 2006). Camacho Inlet presents a history of inlet cross sectional area instability due to its particular environmental conditions; it is typically closed with brief openings during periods of extreme meteorological events (Borderes de Oliveira et al., 2006; Klein et al., 1997, 1998, DEOH - GECO, 1994, DEOH - GECO, 1995, INPH, 1991). The tidal prism of the Camacho lagoon was calculated using methods developed by Metha and Özsoy (1978) (INPH, 1991) at 1,660,000 m 3 . Calculated using O’Brian’s (1969) method, the stable inlet cross sectional area is 175 m 2 , ranging between 56 and 327 m 2 . The minimum cross sectional area calculated using Jarret (1976) methodology it is 127 m 2 (A c ¼ 1.57 Â 10 À4 U 0.95 ). DEOH-GEOCO (1995) measured a cross sectional area of 59.5 m 2 , which is approximately half of the area calculated here. Hydraulic analysis of the inlet reveals that the mean maximum water velocity is not reached (Borderes de Oliveira et al., 2006), possibly explaining some of this discrepancy. The analytically calculated maximal response ability, C R , suggests that even with a 0.03 m minimal amplitude tide, this site will only support an inlet with an A c of 280 m 2 . These data demonstrate that the Camacho inlet cross sectional area is out of equilibrium, explaining why the inlet is only open during extremes events. The Camacho Inlet is located along a wave-dominated coastline with significant wave heights less than 2.0 m 98% of the time (INPH, 1991). Although the most frequent and energetic waves arrive from the south (Araújo et al., 2003), Siegle and Asp (2007) demonstrated that at this site, the coastline orientation diminishes, or even * Corresponding author. Tel.: þ55 48 3231 3421. E-mail addresses: oc.guilhermevs@gmail.com (G. Vieira da Silva), carvalho@ univali.br (J.L.B. de Carvalho), klein@cfh.ufsc.br (A.H. da Fontoura Klein). Contents lists available at ScienceDirect Ocean & Coastal Management journal homepage: www.elsevier.com/locate/ocecoaman 0964-5691/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ocecoaman.2011.04.003 Ocean & Coastal Management xxx (2011) 1e8 Please cite this article in press as: Vieira da Silva, G., et al., Camacho inlet southern Brazil e Instability causes and user conflicts, Ocean & Coastal Management (2011), doi:10.1016/j.ocecoaman.2011.04.003